Teletypewriter switching system



E J. SINGER C. WHITE ATTOR/VE Y m VJCLARGE fil/9X l /NVENTORQ W. V. K.LARGE ET AL TELETYPEWRITER SWITCHING SYSTEM Filed May 15, 1959 Feb. 25,1941.

Patented` Feb. 25, 194i UNITED STATES PATENT OFFICE 2,233,056TELETYPEWRITER swITOHlNG SYSTEM Application May 13,1939, senai No.273,384

11 Claims.

This invention relates to teletypewriter switching systems andparticularly to service observing circuits used in connection .with cordcircuits in manual teletypewriter switching systems. n

An object of thisinvention is to provide a service observing circuit foruse in connection with a cord circuit in a manual teletypewriterswitching system, in which the same supervisory signals as appear in thecord are reproduced in the service observing circuit.

A further object of this invention is to provide a service observingcircuit which is interconnectable with different types of cord circuitsat different times, said cord circuits having apparatus units withbattery of different voltages connected in parallel with apparatus-units in the service observing circuit. n

A feature of this invention is a service observing circuit for` usewitha cord circuit in a man-` ual teletypewriter switchboard, said observingcircuit having a lamp signal corresponding to the cord supervisoryanswering lamp and another corresponding tothe cord supervisory callinglamp, said service observing lamps being arranged to light steadily,Hash or darken in unison with their corresponding cord lamps,reproducing the cord supervisory signals in the service observingcircuit.

A further feature of this invention is a unidirectional current deviceused in a circuit connectable at different times to different types 0fcircuits, wherein the voltages of the connecting circuits are not' thesame, to prevent the false operation of an apparatus uniton one of theYdifferent types of connection.

It is old in the teletypewriter art `to provide means for flexiblyinserting a teletypewriter for monitoring purposesin the transmissionlead of a cord circuit, in series With the teletypewriter switchboardoperators teletypewriter circuit. Such an arrangement is disclosed inPatent 1,884,- 567 to J. J. Catogge, October 25, 1932. Service observingis preferably performed in a separate room out of sight and hearing ofthe operators.

As far as applicants are aware, however, no facilities are available toperform the functions of their circuit herein, namely, to provide aservice observing circuit for cooperating with teletypwriter switchingcord circuits, which, in addition to reproducing the' teletypewritercommunication signals transmitted through the cord, reproduce also thecord supervisory signals. The advantage of this will be`apparenttoanyone skilled in the art, as it not only provides -anindication that the cord circuit supervisory signals are functioningproperly, but furnishes also a check on the manner in which the call ishandled by the operator. This is invaluable in the training of operatorsand in maintaining a high standard of service. In arranging the serviceobserving circuit herein to connect to a cord circuit, instead of to thesubscribers line circuit, a number of advan- -tages over other serviceobserving arrangements are afforded. In observing circuits, in -whichconnections are made to line circuits, it is necessary to provide eitheran entire reappearance of the subscribers line lampsand jacks in thelocation where the service observing is performed, the expense of 'whichis prohibitive, or to make temporary patches to a group of selected linei circuits at various times. These temporary connections areobjectionable for a number of reasons among which are the following: (1)Setting them up and changing them periodically involves expense. (2) Thepatching is generally performed at the distributing frame by means of ashoe and a long -cord which is cumbersome and interferes with the normalwork on the distributing frame. (3) Since a list of numbers of Ithelines which are to be observed must be made up by some operatingoiiicial, such as the chief operator, turned over to the wire chief andthen passed on to the maintenance men, and since anyone who has accesstothe distributing frame may readily observe the numbers of the lineswhich are under observation,

it is difficult to keepv the numbers ofthe observed lines secret. (4)When patch connections are made to selected line circuits, the observingoperators are limited to observing only on calls involving theparticular lines in the selected group. There may be long intervalsduring which the observing operator is'idle awaiting calls in saidselected group.

These difficulties are obviated when the service observing circuit isconnected tothe cord circuit instead of tothe line. The serviceobserving Voperator receives` indications whenever; the

from the following description when read in connection with theassociated drawing.

Fig. 1 is a portion of a cord and operators position circuit used at atelegraph or teletypewriter switchboard in interconnecting telegraph orteletypewriter subscribers, or to extend a subscribers line to a trunkor to interconnect two trunks. The circuit which is well known in theart, has been modied to exibly interconnect with the service observingcircuit of the invention herein;

Fig. 2 is a service observing circuit which interconnects with Fig. 1.'Ilhe observing circuit is used in observing the service provided onconnections established by meansof -the cord circuit per Fig. 1; and

Figs. 3 and 3A are alternative embodiments of a portion of Fig. 2.

It will be assumed that a call is incoming through the answering jack t0the left of Fig. l. In response to the operation of the lamp signalassociated with the jack indicating that a -call is incoming, plug -|0|of Fig. A1 is inserted into the answering jack. A circuit is thereupon`established from ground, through the sleeve of the answering jack,sleeve of plug |0| and winding of relay |02 to battery, operating relay|702.

The ring conductor of the jack is extended through the ring of plug |0|and the ring conductor ofthe cord, through resistance |-25 to the cordcircuitl polar relays indicated by I0. These relays and other portionsof the cord and opera- 'tors position 'circuit which are not shown indetail in Fig. 1 are omitted as they are known in the art and functionin a known manner. Such arrangements are disclosed in numerous patents,

Vsuch as the patent to F. S. Kinkead et al.

2,024,581, December 17, 1935, to which reference is made. The Kinkeadpatent discloses one ernloodiment -of a subscribers *lineA and stationcirthe cord per Fig. l has been used in answering an incoming call.

lIt is to be understood that at any operators position there arenumerous cord circuits, any one of which may be chosen by an operatorthereat in answering and extending a call. Jacks |23 and |24 and theirassociated lamps |2| and |22, respectively, are located at a serviceobserving board which is ordinarily located in a room separate from thatin which the switchboard containing the cord circuits and jacks per Fig.1 are located. All or any part of the cords in the switchboard may besimilarly extended to the observing position so that the observingoperator may observe on any connection handled by the operators at theparticular board being observed upon a particular cost so extended. Incertain cases, such as in large cities where more than one switchboardmay be required and where it is economically feasible, all of the cordcircuits in all of the boards may be connected as indicated in Fig. l toa single centralized service observing board which may be used toobserve on all of the telegraph or teletypewriter switching at thevarious boards in a particular area.

In response to the lamp signal |2| which will light at a particularposition in the service observing board, in front of an operatorobserving on the cord-with which lamp X|2| is associated, the operatorat that particular service observing position will insert double endedplug 20| into Yjack |23 associated with lamp |2| and jack |24 associatedwith the calling end of Fig. 1 and paired with -jack |23 in the serviceobserving board.

When double ended plug 20| is inserted in jacks |23 and |24, thetelegraph signal transmission conductors in the answering end of thecord per Fig. 1 .areopened and the transmission conductors .associatedwith plug 202 in the service observing circuit are connected in seriestherewith. Similarly, the telegraph signal transd mission conductors inthe calling end ofthe cord per Fig. `1 are opened and the transmissionconductors associated with plug 203 in the service observing circuit areconnected in series therewith. These circuits may be traced as follows:From the ring conductor of the answering jack incoming from the callingstation, 'through the ring yor ,middle conductor of plug |01, throughthe tip of jack |23, the Ashunting path through resistance |25, nowbeing open due to the insertion of plug 202, through the tip orright-hand conductor of plug 202, th'e bottom `break contacts of key.204, which contacts are in 4engagement when key 204 is in the normal orunoperated position, through resistance 200, the top break contacts ofkey 204, `which contacts are also `in engagement, the'ring or middleconductor of plug 202, ring 'of Ajack |23 to the polar relays ||0 of thecord circuit. Forth'e calling end of the cord,

the circuit extends 'from the ring or middle conductor of plug |20,`,through the tip or left-hand conductor of jack |24, the shunt paththrough resistance y|20 being 'open due to the insertion of plug 203 injack |24, through thetip'of plug 203, top break contacts of key 205,resistance 201, bottom break contacts 'of `key 201, through the ring ormiddle conductor of plug 203, ring of 'jack`l`24 to the polar relays ||0of the .cord circuit perFig. 1.

The telegraph signal transmission path of each end of the cord circuitper Fig.`l is thus extended into the service observing circuit per Fig.2. By operating key 204 associated with the answeringcnd of the cord,the service observing operator may interconnect rher position circuit inseries with the answering end ofthe cord. Similarly, by operating key205 associated with the -calling end of the cord, the service observingoperator may rinterconnect her position circuit Yin series with thecalling end ofthe cord. When key 204 is operated, the lpath heretoforetraced through resistance 206 is-disconnected at the top and bottombreak contacts of key 204 and the path through the service observingcircuit is substituted therefor. This path may be traced through the topmake-contacts of key 204, winding ofreceiving magnet 208,sending-contacts 209, break key 2|0to the bottom make contacts of key204. Similarly, when key .205 isoperated, the path throughresistance 201is broken at the top and bottom break contacts of `key 205, and theservice observing position is substituted for the resistance through thetop and bottom make contacts, of fkeyf205- :If `it isadesired :to insuresecrecy, sendingcon- `ta'cts 209 and break key 2 0 inthe serviceobserving 4position circuit may be omitted..` 1If it. is desired topermit the observing operator tocommunicate over the circuit as,forinstance, in the training of operators or for some other reasons,these facilities may be included. .nl

vLamps and IIB associated with the answering and calling ends of thecord circuitperllg.,` 1, respectively, are supervisory lamps. They. areused 'to transmit disconnect signals from the calling and calledsubscriber to the operator, as well as Arecall signals from the callingor called subscriber to the operator or recall signals from operator tooperator in the case of aftandem'connection involving a plurality ofswitchboards.

They are also used in certain systems of operation, such asstraightforward systems, inaddtion to providingdisconnect and recallsignals, to indicate successive steps in the establishment "of a callthrough a plurality of switchboards to the called subscriber. `Theselamps may be lighted or fdarkened to convey these signals to theoperator. The invention herein provides means for reproducing thesesignals at the service ob,- serving board, so that the service providedin handling calls may be observed. Essentially, this `is performed byproviding a lamp in the service` observing board connected in parallelwiththe supervisory lamp associated with each end of the 4with theanswering cord may be traced from battery |05 through switch |04, the.filament of lamp |03 to thearmature of relay |01.r For a |09, flashinglamp |00 may be arranged in a large variety of ways,

steady lamp signal, which may serve as a disconnect signal, relay |01 isoperated, responsive to control means, not shown, to connect a steady`flashing lamp signal, relay |01 remains in its released condition, asindicated, and relay |08 is operated, responsive to control means, notshown, .to extend the lamp circuit through the armature Vand backcontact of relay |01 and the front contactl and armature of relay |08,through alternate open and grounded segments of interrupter Theconnections which control relays |01'and well known in the artto providethe steady and flashing lamp signals and, since they form no part of theinvention herein, are not shown in detail. Notwithstanding the manner inwhich these signal conditions may be effected in the cord, however, thesupervisory lamp conductors at eaclnend of the cord are multipled Vintothe `service `observing circuit to reproduce the signal conditions in acorrespondingv lamp associated with each side of the service observing.circuit.

The manner in which this is performed is as- ,filament of lamp 2|2.`Lamp 2|2'is therefore lighted. If a steady ground is connected from Arelay |01, relay 2|lremains operated to main- `tain lamp ,2| 2 steadilylighted corresponding 4to the condition of lamp ih the cord. If aninterrupted ground is connected from Vinterrupter |00botli lamps and 2||will flash simultaneously.1 i.

Thereason why relay 2|| is provided instead Y of .connecting the.filament of l lamp 2|2 directly to the sleeve lead of plug 202 to lightandvextingush the two lamps directly in parallel will now be explained.l 1 n 'Ihere are at present inservice in the existing teletypewriterswitching systems cord` circuits having supervisory lamps operating onbatteries of different voltages. For example, some of the ysupervisorylamps operate on 24 volts and others on 4S' volts. `The polar relaycontrolled lamp in the observing cord makes it possible to provide`observing circuits, having battery voltage ofone value only controllingits lamps, to` function universally with the existing cords havingsupervisory lamps operating on different voltages. The polar relay isarranged to actuate its armature to engage its grounded contact inresponse to current flowing in one direction only. Relay 2li is arrangedto respond to a current flowing' from the positive terminal of thebattery, or ground, to the negative terminal of the battery. It willoperate in parallel with lamp when ground is connected to a common pointintermediate lamp llland relay 2||. The observing `circuit may beconnected to switching cords having negative 48 volt battery connectedto their `supervisory lamps. This may be simulated by operating switch|04 toits alternate contact, to `connect 48 volt negative battery |06Vin series with the filament of lamp For` this condition, even thoughboth relays |01 and |08 are unoperated, sothat the conductor normallyenergizing the lamp circuit is open, `if lamp 2|2 which lights on 24volts were connected directly l to the lamp lead, itv would remainlighted at all ground to lamp lighting the lamp. For a.

times while the plugs 202 were connected to jack |23. This is so becausethe 48 volt battery would preponderate over the 24 volt battery andsufficient voltage would be impressed on lamp 2|2 tomaintain it lightedat all times. This would, of course, be objectionable. The use of apolar relay, such as 2| prevents this from happening, because it willnot respond to current flowing from the negative terminal o-f battery|06.I It will respond, however, when groundy is connected through theoperation of relay |01 or |08 to junction point |21. Thus;v it should beapparent that vthe service observing circuit per Fig. 2 will function`universally with cords 'per Fig. 1 having batteries of differentvoltages connected to its supervisory lamps.

' The supervisory circuit associated with the calling end of the cord,namely, batteries ||8 and ||9,switch ||1, lamps H0 and |22, relays ||3,||4 'and ||5 and interrupter ||2, together with their associated wiringincluding junction |28, function in the identical manner with thatYdescribed Vfor :their corresponding elements in the answering end o-fthe cord.` Similarly, polar relay 2|4, resistance 2|6, lamp 2|5 andtheir connecting wiring; associated with the calling endl of the cordper Fig. 1, function as do their corresponding elements in the serviceobserving circuit associated With the answering end of the cordl perFig. 1.` It is `not considered necessary, therefore, to an understandingof the operation of these elements to repeat this description' as it maybe readily understood from the foregoing by Vthose skilled in the art.

J Fig.`3 is` an alternative embodiment for-the portionof Fig. 2 shown tothe left of dotted line -XX in Fig, 2. In this embodiment a copperoxiderectifying element 30| replaces polar relay 2|| to perform substantiallythe same yfunction as the relay. As is known, such icopperoxide element,when connected in series `in a circuit, presents a low resistance tocurrent of one polarity and a high resistance to current of the oppositepolarity. It is so .connected as t0 present a lo-w resistance to current`flowing from the positive terminal Yor .ground in Fig. 1 throughelement 30| and the :filament of lamp 302 to negative battery. Thus whensteady or interrupted `ground is connected to junction point I 21, lamp302 will light steadily or iiash in parallel :with lamp whether theiilament of lamp be connected to battery |05 or |06. The lamp 302 cannot light when ground is disconnected from junction point |21, eventhough high volt- .age battery |06 be connected in circuit as thecopper-oxide element 30| presents a high resistance to battery .ofnegative polarity connected to its right-hand terminal.

Fig. 3A corresponds to Fig, 3 and is connectable to the portion of theservice observing cir- .cuit cooperating with the calling end of thecord circuit per Fig. l to the right of line YY in Fig. 2'. It isthought unnecessary to repeat its description as it functions in amanner identical with -F-ig. 2A.

What is .claimed is:

1. In a teletypewriter switching system, a teletypewriter cord circuit,a teletypewriter service observing circuit, means in said circuits forinterconnecting said circuits directly, a supervisory signal in saidcord circuit, a signal in said observing circuit corresponding to saidsupervisory signal, and means in said circuits for operating saidsignals substantially in unison.

2. In a manual teletypewriter switching system, a teletypewriter serviceobserving circuit connecting with a teletypewriter cord circuit, a'first signal in said observing circuit, means in said circuits foroperating said signal in unison with a rst supervisory signal in saidcord circuit, 'a second signal in said observing circuit, and means alsoin said circuits for operating said second signal in unison with asecond supervisory signal in said cord circuit.

3. In a manual teletypewriter switching system, a teletypewriter cordcircuit, a teleltypewriter service observing circuit, means in saidcircuits for interconnecting said circuits directly and a visualsupervisory signal in said observing circuit responsive to control meansin a telegraph line circuit connected to said cord.

4. In a manual teletypewriter switching system, a teletypewriter serviceobserving circuit, a visual signal therein and means connected to saidobserving circuit for operating said signal in response to ateletypewriter subscriber disconnect signal.

5. In a manual teletypewriter switching system, a Iteletypewriterservice observing circuit, a visual signal therein and means connectedto said observing circuit for operating said signal in response to ateletypewriter subscriber recall signal.

`6. In a manual teletypewriter switching system, a teletypewriterservice observing circuit, a visual supervisory signal therein and meansconnected to said observing circuit for operating said signal steadilyto indicate a i'lrst condition and intermittently to indicate .a 4secondcondition.

"7. In a'manual teletypewriter switching system,

a Aiirst cord circuit, a first electric apparatus element in saidcircuit, a first battery of a rst polarity ,and of afirst magnitude inelectromotive force connected to said element, a second cord circuit, asecond electric apparatus element in said second cord, .a second batteryof the same polarity .as said first battery and of a second .magnitude.in electrornotive force, substantially different from said firstmagnitude, connected 'to saidsecond element, a monitoring circuitarranged :to cooperate independently and interchangeably with said rstand second cords, a 'third electric apparatus element in said monitoringcircuit, a third battery of the same polarity, and same magnitude inelectromotive force as Vsaid first battery connected to said element,means in said circuits for connecting said first .element iniparallelwith said third element at a first time, means also in said circuits forconnecting said second element in parallel with said -third element at asecond time and a unidirectional current device in series with saidthird .element to .prevent the energization of said third Velement dueto said diierence in magnitude.

8. In a teletypewriter switching system, a first lamp filament, abattery of a iirst polarity and ci `a first magnitude electromotiveforce connected Ebetween ground and a first end of said `filament, asecond lamp filament, a battery of said first polarity and of a secondmagnitude electromotive force, substantially greater than lsaidfirstmagnitude, connected between ground and a iirst end of said secondfilament, a con- -ductor `connecting the second ends of said filafrnentsanda unidirectional current device connected .in series .in saidconductor to prevent the heating of said filaments dueto said diiierencein magnitude.

9. A circuit having a lamp larnent connected in parallel with thewinding of a polar relay, opposed batteries o-f substantially differentvoltages connected individually to said lament and :said relay, means insaid circuit for maintaining said lamp filament darkened and said relaywinding venergized in a first manner for a first condition and meansconnected to said circuit for maintaining said lainent lighted and saidwinding energized in a second manner for a second condition.

10. In a teletypewriter switching system, a'

in Yresponse to said connection to indicate that i said connection hasbeen established, a teletype-l Writerservice observing circuit, flexibleswitching means in said kcord and observing circuits for manuallyinterconnecting said cord and observing -circuits in response to saidsignal, a supervisory signal also in said cord operating in respouse tocontrol means in said calling circuit, a signal in said observingcircuit corresponding to said supervisory signal and means in saidcircuit for-operating said corresponding signal substantiallysimultaneously -with said supervisory signal.

11. In a teletypewriter switching system, a .manual teletypewriter cordcircuit, means in said circuit for connecting said cord to a calledteletypewriter circuit, a signal in said cord at a teletypewriterservice observing position operating in response to said connection toindicate that said connection has been established, a teletypewriterservice observing circuit, ilexible switching means Vin said cord andobserving circuits for manually interconnecting said cord and observingcircuits in response to said signal, a supervisory signal also in saidcord operating in response to control means in said called circuit, asignal in said observing circuit corresponding to said supervisorysignal and means in said circuits for operating said correspondingsignal substantially simultaneously with said supervisory signal.

WAYNE V. K. LARGE. FRED J. SINGER. CHARLES WHITE.

